Ask A Scientist Chemistry Archive

name         Steve S.
status       other
age          40s

Question -   I am building a pond with several waterfalls and water
features in Ridgeway, Colorado, at an elevation of 9000 feet. I have heard
you can prevent the water from freezing by adding salt to the water. Is
there a formula that I can follow, per gallon, or other measurement, to
allow the water to run year round?

-------------------------
Steve,

You did not specify the volume of water to be treated or the minimum 
temperature
to which it will be exposed. The amount of salt required depends on this
information.

Given the corrosiveness of salt toward pumps, plumbing, and the pond liner and
stones, why use it at all? Consider recreational vehicle water-supply and 
waste
tank winterizing antifreeze (available almost everywhere) because it is
non-corrosive and non-toxic. The ratio of antifreeze to water is usually
printed on the container.

Regards,
ProfHoff 353
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You can find the detailed data about the freezing point depression of
various substances in "The Handbook of Physics and Chemistry" published by
Chemical Rubber Company, which will likely be found in the reference section
of your library.

To give you some feel for what to expect: a 5% solution of NaCl melts at -3
C,
a 10% solution melts at about -6.5 C. You will find data on other salts and
organic solutes as well. I think you will have a serious problem with
corrosion, however.

Vince Calder
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